Whats the average gas mileage everyone is gettin with a 350 in a full size truck or jeep, with 3 speed trans.

Reason I ask is im guessin what i have will get similar. I have a TJ with 350 bored .40 over, i believe stock cam, 305 heads, edelbrock 4 barrel carb either 600 or 650 i forget at this point, TH350, 4.10 gears and 33" tires, tryin to decide to D.D. it or keep letting it sit and drive a few times a year because i dont have the time to take it out offroading much anymore. It gets pricey to insure 3 vehicles for 9 months out of the year, i would like to cut one out of the equasion.
I cant check my gas mileage at this exact moment, speedo is way off and i tried to top off the tank today and found out the filler neck dumped a bunch of gas to the ground from the top of the tank as soon as it filled all the way.

Doing 70mph (according to gps) tach is at 3200 rpm, Am considering changing axles to a 3.55 or something to lower my rpms a bit.

A good tune, solid engine, 3.55 or lower gears (depending on tire size), and a light foot will get mileage in this range. Fuel injection is also a big benefit.

Well i shure hope the engine is solid and tuning is good. (well atleast i think soo and everyone else does.)
I have a MSD box im waiting to put on there also, i just haft to buy a new distributor, coil, plugs, and wires first.. Im guessin that wont hurt me though.

Obviousley i know if i step on it ill be just pouring gas away, but thats beside the point.

You can get that if your nice to it. 70 mph on a 3 speed starts to use a lot of fuel. 65 is wwwaaayyy better for gas mileage

yeah i know that will help also. and well ill try, just it hard letting little smart cars and semi trucks pass me...

right now im kinda just lookin for a base average. obviousley if dropping 5mph will help me durastically i will, but im coming from cruse-control always set at 78 to 79 in the left lane down to 70 in the right lane its pretty rough.

Helps if you have a properly adjusted vacuum distributor, and like always with any vehicle, brakes are the enemy of fuel mileage. Depending on what lift and also what air/fuel ratio its running at, its no problem to get 15-18 mpg. Lots of factors just than these also. Give it a try